The present invention pertains generally to a disposable contact lens for use in laser surgery. More specifically, the present invention pertains to a contact lens that is useful for stabilizing the eye during laser ophthalmic surgery. The present invention is particularly, but not exclusively, useful as a contact lens which can be positioned against the eye to accurately align the eye with a laser source during ophthalmic laser surgery.
It is well known that many advancements have been made in the area of ophthalmic surgery in recent years. In particular, it has happened that lasers are being more frequently used to perform certain ophthalmic surgical procedures. With presently used laser systems, however, it is a critical concern that the eye be accurately positioned in a predetermined relationship relative to the laser system. It is only when the eye can be accurately positioned relative to the laser system, that the laser beam can then be directed to the desired area inside the eye with a high degree of accuracy. This is important because an inaccurately or improperly directed laser beam could affect an unwanted area of the eye and cause permanent damage to the eye.
One way to accurately position the eye relative to a laser system, for the purposes of performing laser ophthalmic procedures, is to use a contact lens which will stabilize the eye. To do this, however, the contact lens itself must be accurately aligned with respect to the laser source. As indicated above, if the lens is not properly positioned relative to the laser source, errors in accurate positioning of the laser beam can result.
In order to ensure a correct alignment of a contact lens with a laser system, it is possible to permanently mount the lens on the laser source in a fixed orientation. If the contact lens is to remain mounted on the laser system, however, sterilization of the lens after each laser ophthalmic procedure could be time consuming, difficult to accomplish and, most likely, very uneconomical. Alternatively, the contact lens could be removed from the laser system, sterilized and replaced. Further, a disposable contact lens could be used for the laser ophthalmic procedure. For either of these last two alternatives, however, the contact lens will require realignment with the laser system after the lens is mounted on the laser system.
With the above in mind, it is an object of the present invention to provide a contact lens for laser ophthalmic surgery which can be quickly and efficiently mounted on a laser system. Another object of the present invention is to provide a contact lens which will accurately position and stabilize the eye relative to a laser system for laser ophthalmic surgery. Still another object of the present invention is to provide a method for aligning a contact lens with a laser system. Yet another object of the present invention is to provide a disposable contact lens for use in ophthalmic surgery which can be replaced with another similar contact lens. Another object of the present invention is to provide a method for mounting a contact lens on a laser system for use in ophthalmic surgery which will consistently align the lens to a predetermined orientation relative to a laser beam. Another object of the present invention is to provide an contact lens for laser ophthalmic surgery which is effectively easy to use, relatively simple to manufacture and comparatively cost effective.
In accordance with the present invention, a disposable contact lens for use in laser ophthalmic surgery includes a mechanism and a method for accurately aligning a laser system with the contact lens. With specific regard to the laser system of the present invention, this component generates a pulsed laser beam which has pulse durations that are chosen in a range of less than approximately three hundred picoseconds ( less than 300 ps). Additionally, the laser beam has a wavelength that is selected from the range of approximately 0.4-1.9 micrometers (0.4-1.9 xcexcm). In order to be effective for the purposes of the present invention, this laser system must be capable of establishing a predetermined spatial relationship with the eye of a patient.
In accordance with the present invention, the position of the laser system is based on measurements of the laser beam. Specifically, the origination point of the laser beam in the laser system is known. The laser beam can then be directed from the origination point along at least three predetermined paths. Further, the laser beam can be focused to respective predetermined focal points on each of these paths. Together, these predetermined focal points can then be used to define an alignment plane for the laser system. Once the alignment plane is identified, the contact lens then needs only to be oriented on this alignment plane in order for the contact lens to be properly positioned relative to the laser system. In order to do this, however, it is also necessary to identify a characteristic reference for the contact lens.
The contact lens of the present invention is preferably made of a clear medical grade plastic and has at least three reference marks which are placed on one of its surfaces. In the preferred embodiment of the invention, the three reference marks are placed equidistant from each other and are located near the periphery of the lens surface. Importantly, the laser system based reference (i.e. the predetermined focal points) and the contact lens based reference (i.e. the reference marks on the contact lens surface) must be compatible. Therefore, the reference marks are placed on the lens so that they will be coincident with the predetermined focal points of the laser beam when the contact lens is properly aligned with the laser system.
To engage the disposable contact lens with the laser system, the contact lens is mounted on a retainer ring that is affixed to the system. More specifically, there are three adjusters that interconnect this retainer ring with the laser system which, in concert, can be operated to adjust the position of the retainer ring relative, and hence the contact lens, to the laser system. Importantly, the retainer ring also positions the contact lens to intersect the predetermined paths of the laser beam.
With the contact lens mounted on the retainer ring, the laser beam is focused to a focal point on the surface of the contact lens. Once so focused, the laser beam is activated to etch a laser mark onto the surface. This process is repeated for each of the three predetermined paths to establish three laser marks on the surface of the contact lens. Recall, the reference marks on the contact lens are respectively coincident with the predetermined focal points of the laser beam when the contact lens is properly aligned with the laser system. It then follows that if the laser marks are coincident with the reference marks, the contact lens is in proper alignment. On the other hand, it there is any displacement xcex94 between a reference mark and its respective laser mark, then the contact lens is somehow tilted relative to the laser system. Stated differently, the lens plane and the alignment plane are not coplanar. To align the lens to the laser system for laser ophthalmic surgery, the lens must then be moved to make all reference marks on the contact lens coincident with their respective predetermined focal points.
As implied above, the length of the adjusters can be modified automatically by a control system to tilt the contact lens into alignment with the laser system. To do this, the control system will receive an input signal that is indicative of a displacement xcex94, between each reference mark and its respective laser mark. This input signal, which represents the measurable displacement xcex94 values, is then compared with known geometric relationships which are preprogrammed into the control system to generate an error signal. The control system then appropriately changes the lengths of the adjusters to tilt the retainer ring into an alignment position, and thereby minimize the error signal.